全文获取类型
收费全文 | 1654篇 |
免费 | 32篇 |
国内免费 | 322篇 |
专业分类
化学 | 1647篇 |
晶体学 | 16篇 |
力学 | 22篇 |
综合类 | 5篇 |
数学 | 25篇 |
物理学 | 293篇 |
出版年
2024年 | 2篇 |
2023年 | 41篇 |
2022年 | 27篇 |
2021年 | 49篇 |
2020年 | 33篇 |
2019年 | 45篇 |
2018年 | 54篇 |
2017年 | 56篇 |
2016年 | 66篇 |
2015年 | 54篇 |
2014年 | 92篇 |
2013年 | 129篇 |
2012年 | 90篇 |
2011年 | 105篇 |
2010年 | 97篇 |
2009年 | 117篇 |
2008年 | 104篇 |
2007年 | 105篇 |
2006年 | 103篇 |
2005年 | 89篇 |
2004年 | 70篇 |
2003年 | 51篇 |
2002年 | 44篇 |
2001年 | 37篇 |
2000年 | 25篇 |
1999年 | 27篇 |
1998年 | 29篇 |
1997年 | 21篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 14篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 23篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有2008条查询结果,搜索用时 15 毫秒
1.
N. U. Aldiyarov K. K. Kadyrzhanov E. M. Yakushev V. S. Zhdanov 《Hyperfine Interactions》2005,164(1-4):67-72
The conditions for achievement of high resolving power of depth selective conversion electron Mössbauer spectroscopy method at a combined installation ‘electron spectrometer–nuclear gamma-resonance spectrometer’ have been obtained. There has been made a considerable step in development of the method at its realization at a magnetic sector electron spectrometer with double focusing, equipped with electron source (a sample under investigation) of large-area and position-sensitive detector. The paper presents a prospective symmetrical version of a magnetic sector electron spectrometer that allows realizing more completely possibilities of the method. It is noted that the proposed method is particularly valuable for investigations of nanosystems, nanostrutures that contain Mössbauer nuclei. 相似文献
2.
描述了简并V型三能级原子与单模相干态光场的Raman相互作用,获得了处于激发态单态的原子与相干态光场相互作用的结果.利用探测原子与光场的相互作用将原子和光场制备成最大缠结态,并注入待测原子,通过原子与腔模构成的Bell基矢演化,对腔场进行选择性探测,获得探测原子相互作用后可能的量子状态,然后对待测原子与腔场进行联合探测,接着对探测原子的量子状态实施幺正变换,就将探测原子制备到待测原子的初始量子态上,从而实现未知原子态的隐形传送. 相似文献
3.
A simple procedure for the synthesis of an important standard, isotopically enriched methylmercury, which is not commercially available, has been established successfully. The isotopically enriched standard synthesized is utilized in conventional isotope dilution mass spectrometry (IDMS), as well as in speciated IDMS (SIDMS), for determination of the true concentration of methylmercury in environmental samples. The CH3201Hg+ standard has been synthesized from commercially available 201HgO and tetramethyltin. The synthesis time required is 1 h at 60°C. The product is highly pure, yielding more than 90% as 201Hg in CH3201Hg+. Hazardous dimethylmercury does not occur during this synthesis procedure. The product synthesized was analyzed using high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP‐MS) and ICP‐MS alone in order to determine its concentration, isotopic composition and purity. The stability of the product was also evaluated for over 6 months and found to be stable at 4°C in the dark. The isotopically enriched methylmercury synthesized can be used in SIDMS and IDMS analyses as a standard. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
A method has been developed to determine the boiling point distribution of sulfur compounds in light cycle oils (LCO'S). The method chosen for this analysis was GC with a flame photometric detector (FPD) and pyrolyzer. Tests were carried out to evaluate the recovery efficiency, repeatability, and accuracy of the method. Repeatabilities within 2% were obtained. The recovery of benzothiophenes and dibenzothiophenes was close to 100%; this was important because these are the major sulfur components in LCO's. No hydrocarbon or solvent interferences were observed with the use of the pyrolyzer, even for a 95% solvent level. Comparison with results from other techniques showed that the method accurately determined the levels of sulfur compounds in the LCO boiling point range. 相似文献
5.
6.
Summary A new gas chromatographic method using an automatic purge-and-trap system coupled to a GC with mass selective detection to analyze styrene at the parts-per-trillions (ng kg–1) level is described. The method shows a good sensitivity and the detection limit is 10 ng kg–1 with a relative standard deviation (RSD) of 4.7% for 164 ng kg–1 styrene in olive oil. This analytical method has been successfully applied to the analysis of styrene in extra-virgin olive oil from the European market. 相似文献
7.
ZHU Hai-Xia YAN Shi-Lei 《理论物理通讯》2004,42(11)
We study the ferromagnetic properties of spin-1 system, which is considered in the frame of the bond dilution and random positive or negative anisotropy Blume-Capel model in the effective field theory and a cutting approximation. The investigation of phase diagrams displays some rich properties of the trajectory of tricritical point, reentrant henomena at low temperatures. Under certain both bond concentrations and random negative anisotropy, there are new transition lines of double tricritical points. So special emphasis is placed on the influence of the bond dilution and random anisotropy on phase diagrams. The magnetizations of the system are also discussed. Some results have not been evealed in previous reports. 相似文献
8.
9.
苯部分加氢制环己烯的非晶态Ru-M-B/ZrO2催化剂的表征 总被引:13,自引:0,他引:13
采用化学还原法,制备了高活性,高选择性非晶态RU-M-B/ZRO2催化剂,并将其用于催化苯部分加氢制环己烯,在140℃、5.0Mpa氢压下,苯转化40%时,环己烯选择性达到85%左右。环己烯最高收率达到52.1%,用XRD、SEM、BET比表面积测定等手段对摧化剂进行表征,XRD和SEM测试表明,RU-U-B/ZRO2属于非晶态,活性组分高度分散,XRD结果证实,在加氢过程中,非晶分解,RU晶化;温度愈高,RU晶化愈快,催化剂的活性、选择性与RU微晶的粒径有关,RU微晶粒径应控制在5nm左右,BET比表面积测定表明,ZRO2的负载提高了催化剂的比表面积,从而有利于活性组分的高度分散,并可阻止RU微晶的长大,讨论了B和ZRO2对提高选择性的作用。 相似文献
10.
同位素稀释-火花源质谱法分析人参样品中微量元素 总被引:2,自引:0,他引:2
本文采用同位素稀释-火花源质谱法定量分析了吉林野山参,园参及高丽参中30多种微量元素的含量。测定下限2μg/g,相对标准偏差在5~28%以内。 相似文献